Alecto and Amycus are two of the Death Eaters who were summoned after Lord Voldemort's rebirth. While their names are not mentioned by Voldemort, their membership in that group is strongly implied by Snape's comments in the early chapters of Harry Potter and the Half-Blood Prince.

The Carrows take part in the attack on Hogwarts. Both of them are at the top of the tower when Snape kills Albus Dumbledore. Amycus showed disdain for the headmaster and wondered why Voldemort was even bothering to have him killed. During the Death Eater's escape, Amycus was seen overwhelming Ginny Weasley before being repelled by Harry. He was later ordered by Snape to retreat. He is later seen leaving the grounds along with his sister and Thorfinn Rowle.

With Snape being appointed Headmaster, and Charity Burbage having been killed, there are vacancies for Defence Against the Dark Arts and Muggle Studies teachers. Amycus Carrow is given the post of Defence Against the Dark Arts teacher, and supervises its change of focus to remove the Defence aspects of the course. According to Neville Longbottom, under the supervision of Amycus Carrow the students were forced to perform horrible acts such as practicing the Cruciatus Curse on people who had earned detentions.

Amycus' sister Alecto, told by Lord Voldemort to expect Harry to visit Ravenclaw Tower, has herself let into the Ravenclaw common room before Harry's arrival. She is then Stunned by Luna Lovegood, who was accompanying Harry under the Invisibility Cloak. Amycus, responding to her summons (Alecto has pressed her Dark Mark, to summon Voldemort), demands to be let in, but is unable to answer the riddle posed by the eagle's-head knocker guarding the door. Having been let in by Minerva McGonagall, he finds his sister Stunned, and proposes to blame it on the students of Ravenclaw. McGonagall refuses to countenance this, Amycus spits at her, and Harry, outraged, hits Amycus with the Cruciatus curse. When he regains consciousness, McGonagall places him briefly under the Imperius curse, forcing him to give her his and his sister's wands, then lie down beside his sister, whereupon McGonagall binds them both. He takes no further part in the story.

Amycus Carrow seems to have brute strength, and we can assume better than average skill in the Dark Arts and offensive spell casting, as shown by Voldemort assigning him the position as Dark Arts teacher and the fact that he seemed to have no trouble overpowering Ginny Weasley in a duel.

Amycus is not particularly intelligent; he is unable to enter Ravenclaw tower, as he is unable to propose an answer that the eagle-head guardian will accept. His initial response seems to be brute-force, and eventually he forces Professor McGonagall to open the door for him.